Synthetic lubricants



P'atented Aug. 14, 1956 United States Patent fire 2,758,975

simple or mixed carbonate depending on the character 2,753,975 of thesecond alcohol. The equation is as follows: SYNTHETIC LUBRICANTS ROH Fil 0 Dehner L. Cattle, Highland Park, Frederick Knoth, in,Chlomiormic'ester Sayreville, and David W. Young, Westfield, N. J.,assignors to Esso Research and Engineering Company, H01 a corporation ofDelaware ll 1 No Drawing. Application July 2, 1952, Carbonate Serial No.296,934 The organic carbonates which may be used for the 4 Claims252-493) purposes of the invention have the general formula ROCOOR'wherein R and R are hydrocarbon radi- The present invention relates toorganic materials usecals having at least 8 carbon atoms. While thisbroad ful as synthetic lubricants and for various other purposes. groupof compounds has utility in the fields of synthetic More specifically,the invention pertains to improved synlubricants and plasticizers, thoserepresentatives of the thetic materials having excellent lubricating andplastigroup which have pour points below F. and flash cizing propertiesand to methods for making these 1113- points above 300 F. have beenfound to be most suitterials. In its broadest aspect, the inventionprovides 20 able as lubricating oil bases in general and for the proforthe manufacture of lubricants and other valuable duction of lowtemperature greases in particular. materials, such as plasticizers forresins, rubbers, etc. on In accordance with the preferred embodiment ofthe the basis of certain organic carbonates having the generalinvention, the carbonates used have branched-chain hyforrnula ROCOOR'.drocarbon radicals R and R, each radical containing at Prior to thepresent invention it has been suggested least 8 carbon atoms. Thesecompounds may be obto use certain synthetic oils, particularly certainesters tained by reacting phosgene with branched-chain monoof dibasicaliphatic acids as an oil constituent for greases, hydric or polyhydricalcohols in the manner described engine oils, extreme pressurelubricants and related maabove. Examples of such carbonates are thosederived terials. While lubricants prepared on the basis of these from6-methyl-l-heptanol, Z-n-propyl-l-pentanol, 3-nesters have highlydesirable lubricating qualities as well 3 propyl-l-hexanol,2,2-dimethyl-l-octanol, 10,10-dimethylas excellent high and lowtemperature characteristics, l-undecanol, 3-isopropyl-l-heptancl.

many of these esters are easily hydrolyzed. In addition, However, it hasfurther been found that good results the field of available rawmaterials is rather limited. In are consistently obtained when using agroup of new carview of the rapidly increasing demand for syntheticbonates which are derived from the product or bylubricating oils in manyfields, a broadening of the raw product alcohols of the well known OX0synthesis. material basis is highly desirable. Similar conditions J Thisprocess involves the catalytic reaction of olefins prevail in the fieldof plasticizers and related materials. with carbon monoxide and hydrogenat elevated tempera- It has now been found that certain organiccarbonates tures of about 300400 F. and pressures of about2500 may besubstituted for low boiling mineral oil fractions to 4000 p. s. i. g. toform, particularly in the presence and synthetic oils of the typedescribed above in the mo of cobalt catalysts, aldehydes having onecarbon atom duction of lubricants, plasticizers and for various other 40more than the olefin originally used. The aldehyde is uses. Thesecarbonates have excellent lubricating qualicatalyn'eally hydrogenated tothe corresponding alcohol ties and combine relatively high boilingpoints with dewhich is recovered as overhead product by distillation ofsirably low pour points, high flash points, low viscositythe reactionmixture. The distillation residue, i. e. the temperature coefficientsand high chemical stability. so-called Oxo-bottoms, is rich inby-product alcohols Organic carbonates may be prepared by contacting ofhigher molecular weight. phosgene with a suitable alcohol attemperatures of about While the exact composition of all these alcoholsis 260 to 350 F. Phosgene may either be bubbled through not known, it iswell established that they are mixtures the alcohol maintained atreaction temperatures or the of primary alcohols, at least a substantialproportion of phosgene may be dissolved in a solvent, such as toluene,which is of the branched-chain type. The overhead and the alcohol addedto the solution maintained at realcohol product consists of a mixture ofsuch alcohols action temperatures, preferably in the presence of a base,averaging 1 carbon atom more than the olefin originally e. g. a tertiaryamine such as trimethyl or triethylamine, fed to the Oxo synthesis. Ithas been found that these dimethylaniline, pyridine or an inorganic basesuch as alcohols may be reacted with phosgene as described alkali metalhydroxides or carbonates. above to produce new carbonates of the generaltype The process may be carried out in stages as follows. defined above.Oxo-alcohol carbonates which have The chloroformic ester of the alcoholused may first be branched-chain hydrocarbon radicals containing atleast formed by adding 1 mol of alcohol to 1 mol-of phosgene 8, andpreferably 10-20, carbon atoms each are preferred as described above.Thereafter, 1 mol of the same or for the purposes of the presentinvention. of a different alcohol may be added to this chloroformicNovel carbonates having excellent properties for the ester, preferablyin the presence of a base to form a purposes of the invention may beobtained by the reaction of phosgene with Oxo-alcohols produced byreacting polymers and copolymers of C3 and C4 monoolefins in thepresence of oxonation catalysts as described above. Suitable mixtures ofthese mono-olefins are readily available in refinery gases and processesfor their conversion into liquid copolymers are well known in the art.In accordance with the most widely used of these processes, the olefinsare contacted in liquid phase with a polymerization catalyst comprisingphosphoric acid supported on kieselguhr. Other similar processes use ascatalyst silica gel impregnated with phosphoric acid, or sulfuric acid,Friedel-Crafts catalysts, activated clays, and others. Polymerizationconditions in the presence of phosphoric acid catalysts includetemperatures of about 300 500 F. and pressures of about 250-5,000 p. s.i. g. The olefinic feed stocks normally contain about l5-60 mol percentof propylene, about 05-50 mol percent of butylenes and from 01-10 molpercent of isobutylene, the remainder being saturated hydrocarbonshaving 2-4 carbon atoms per molecule. In place of or together with theseolefin mixtures the dimer and trimer of isobutylene as well as tri,tetra and penta propylene may be used.

The composition and structure of the C8 Oxo-alcohols obtained from amixture of C7 olefins of the type described above and more specificallyof C7 olefins derived from a refinery gas stream containing propyleneand mixed normal and iso-butylenes "are now well understood. TheseOxo-alcohols have the following analysis:

Structure of C3 Oxo-alcohols prepared from -04 copolymer Percentheptenes F i OCCCCOOH 29 i t CCCOCO-O-H 25 t i CCC-CCCOH 17 (I)COO-O-C-CGOH 16 C CCCGCC-OH G I i CCC-CCO-OH 2. 3

(I) C(iCCCC-OH 1. 4

2-alkyl-alkanols 4. 3 Others 5. 0

Total. 100. 0

Other Oxo-alcohols are believed to have compositions generally analogousto that specified above, chain lengths and degree of branching dependingon the type of olefins used. It is noted in this respect that even whenpure straight-chain olefins are used as the starting materials, thealcohols obtained consist predominantly of branched-chain compounds.

Examples of carbonates having utility as lubricating oil bases,plasticizers, etc. are tabulated below together with some of their moreimportant characteristics.

Viscosity in centi- Pour, Flash, stokes at- Garbonate of- T. F.

C10 0x0 alcohol 75 355 2. 43 9. 27 01; 0x0 alcohol. 410 4. 32 23. 8 Cu0x0 alcohol 40 455 8.32 78. 6

The addition of some polymers improves the viscosity of the 0x0carbonates as shown in the table below.

Other carbonates having similarly desirable properties include thoseotbained by reacting phosgene with 0x0- alcohols to form di-isooctylcarbonate and diisoundecyl carbonate.

Some of the critical properties of carbonates prepared from OX0 alcoholsin the manner described above are tabulated below in comparison withthose of some prior art mineral and synthetic lubricants.

Viscosity in centistokes at- Lubricant Prepared by 0x0 synthesis from-Pour Flash Di'Oi 0x0 adipate C1 copolymer of butylene and propylene- 4002. 81 9. 84 Di-Cm 0x0 adipate Co polypropylene- (75 465 4. 70 20. 83Specifications for complex ester-type of lubricating oil 60 470 10. 152. 0 Extracted Mid-Continent mineral oil 5 410 4. 99 29. 8 Carbonate of(13 0x0 alcohol 0n polypropylene 70 410 4. 82 23. s Carbonate of C" 0x0alcohol c polypropylene 40 465 8. 32 78. 6

The above table shows that the new Oxo carbonates of the inventioncompare favorably with synthetic lubricants as well as mineral oils.

These carbonates may also be used as plasticizers. The results on Mooneyviscosity for C13 Oxo carbonate in GR-I butyl rubber(isobutylene-diolefin copolymer) and GR-S styrene butadiene copolymerrubber are recorded in table form below.

It is to be noted that the C13 Oxo carbonate at 25% as well as at 50%concentrations reduces the Mooney viscosity value of these rubbers at212 F. to a very low value. The preferred range of plasticizer in theserubbers is about 1530%. Good results have also been obtained when addingC13 Oxo alcohol carbonate to ethyl cellulose. The carbonate iscompatible with ethyl cellulose and acts as a plasticizer for the latterin concentrations as low as 10% As to other specific uses, extremepressure lubricants may be produced by incorporating small percentages,e. g. 230 wt. percent of an extreme pressure agent containing sulfur,phosphorus and/or halogen, such as well known hydrocarbon derivativescontaining both active halogen and active sulfur into the carbonates ofthe present invention. Carbonates such as those of the C10 to C16 Oxoalcohols are particularly suitable for this purpose.

For example, when 3% of tri cresyl phosphate was added to the carbonateof C16 Oxo alcohol the lubricant carried all 15 weights on the Almenmachine, under both gradual and shock loading conditions.

Lubricating greases in accordance with the invention may be prepared byincorporating into the carbonate grease-making proportions, say about5-40 wt. percent of a suitable metal soap, preferably an alkali oralkaline earth metal soap of a high molecular weight fatty acid having30 carbon atoms per molecule or of a soapsalt complex consisting of thesoaps of higher molecular Weight fatty acids and the salts of lowmolecular weight fatty acids, such as acetic, furoic, acrylic, orsimilar acids. The metal soap or soap-salt complex may be added as suchparticularly when carbonates are used which contain hydrocarbon radicalshaving only 5 carbon atoms or less which have a strong tendency tohydrolyze at soapforming conditions. In this case, the preformed drysoap or complex may be slurried into the carbonate and the mixtureheated to 300 500 F. while stirring until a homogeneous mass is obtainedwhich is cooled to form the finished grease.

The preparation of greases in accordance with the invention will beillustrated by the following example.

A C13 Oxo alcohol produced by catalytic oxonation of C12 olefin polymerwas converted into the carbonate as follows: Phosgene was bubbledthrough the alcohol which was heated to 284 F. until HCl evolutionceased. The product was washed with water, hydrochloric acid and sodiumhydroxide solutions and distilled, the fraction distilling at 338360 F.at 7 mm. pressure being taken as product. This carbonate had thefollowing properties:

A lubricating grease of excellent stability was prepared as follows:

Ingredients: Wt. percent Complex lithium soap 20 C13 0x0 carbonate Forpreparing the complex lithium soap, a mixture of acetic acid andhydrofol acid (hydrogenated fish oil acids) in a 1:1 mol ratio wasconeutralized with lithium hydroxide. The finished dry soap contained asmall excess (about 1.0%) of free alkali.

The preformed dry soap was slurried in the carbonate and then stirredwhile heating to 450 F. The fluid molten grease was cooled withoutfurther agitation. The finished product was extremely hard and tended tobecome crumbly on homogenization. The soap concentration was furtherdiluted with an equal weight of carbonate and reheated to 450 F. andallowed to cool. The finished inhibited grease had the followingformulation:

ingredients:

Complex lithium soap 9.0 wt. percent. C13 Oxo carbonate 90.0 wt.percent.

Phenyl alpha naphthyl- 1.0 wt. percent.

amine oxidation inhibitor. inspection and properties:

Dropping point, F. 360. Penetrations,77F.mm./10:

Unworked 265.

Worked, 60 strokes 285. Worked, 60,000 strokes 290.

Water solubility Insoluble.

Appearance S m o o t h uniform, homogeneous grease. Light homogenizationhowever results in greater smoothness.

It is noted that the above grease-making example is presented toillustrate the utility of the carbonates of the present invention as asynthetic lubricating oil base. Greases based on the carbonates of thisinvention and processes for preparing such greases are claimed anddescribed in greater detail in the copending Morway, Cattle and Youngapplication, Serial No. 296,935, filed of even date with the presentapplication and assigned to the same interests.

The invention is not limited to the specific figures of the foregoingexamples. The relative proportions of the materials used may be variedwithin the limits indicated in the specification to obtain products ofvarying characteristics.

What is claimed is:

1. A synthetic lubricating composition which comprises a majorproportion of a mixture of organic carbonates of the formula wherein Rand R are branched chain alkyl groups derived from C10 to C20 alcohols,containing combined therein a minor but extreme pressure-improvingamount of tricresyl phosphate, said mixture of organic carbonates havinga pour point below about 20 F. and a flash point above about 300 F.,said alcohols being predominantly isomeric mixtures of branched-chainsaturated aliphatic primary alcohols.

2. A synthetic lubricating composition according to claim 1 wherein saidalkyl groups contain from about 13 to about 16 carbon atoms.

3. A synthetic lubricating composition according to claim 1 wherein saidalkyl groups contain about 13 carbon atoms.

4. A synthetic lubricating composition according to claim 1 wherein saidalkyl groups contain about 16 carbon atoms.

References Cited in the file of this patent UNITED STATES PATENTSMitchell Aug. 9, 1927 Kvalnes Aug. 24, 1937 Dickey et a1. Apr. 4, 1939Wojcik Dec. 21, 1943 Knutson et a1. Feb. 1, 1944 OTHER REFERENCES Ind.and Eng. Chem, vol. 39, No. 4, pages 491-497. Ind. and Eng. Chem, vol.42, No. 12, pages 2422, 10 2423, and 2426.

1. A SYNTHETIC LUBRICATING COMPOSITION WHICH COMPRISES A MAJORPROPORTION OF A MIXTURE OF ORGANIC CARBONATES OF THE FORMULA